Determination of proton electromagnetic form factors from DVCS measurements

TL;DR

This paper analyzes proton electromagnetic form factors using exclusive photon leptoproduction data, demonstrating that such measurements can complement traditional methods and help refine the proton charge radius with a new analytical framework.

Contribution

It introduces a novel analysis method for extracting proton form factors from EP data, providing a unified approach to combine EP and elastic scattering results.

Findings

EP measurements constrain F1(t) in certain t-range.

Extracted charge radius is smaller than traditional scattering results.

EP data can complement elastic scattering in proton structure studies.

Abstract

We present a detailed analysis of the proton electromagnetic form factors (FFs) using exclusive photon leptoproduction (EP) data in kinematic regions where the Beth-Heitler (BH) contribution dominates the deeply virtual Compton scattering (DVCS) cross section By exploiting the sensitivity of the BH amplitude to the Dirac and Pauli FFs, we extract $F_{1}(t)$, $F_{2}(t)$, and the corresponding Sachs FFs within several fitting scenarios based on dipole and $P$-pole parametrizations, and evaluate the charge and magnetic radii of the proton. In this fitting scenario, we show that EP measurements in the range $0.11 < |t| < 0.45~\mathrm{GeV}^2$ can provide constraints on $F_1(t)$, while offering limited sensitivity to $F_2(t)$. The extracted charge radius values tend to be smaller than those obtained from traditional elastic electron-proton scattering measurements and are consistent, within uncertainties, with recent hig-precision PRad results. These findings indicate that EP measurements, especially when covering smaller values of $|t|$, can serve as a complementary tool for determining the proton electromagnetic structure and may contribute to ongoing efforts to better understand the proton charge radius.The methodology developed here provides a framework for future combined analyses of EP and elastic electron-proton scattering data which enables a unified determination of the nucleon FFs.